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961.
We present a comparison between calculated densities of states of the Laves phase MgZn2 and hexagonal Mg28Zn65Y7 and experimental results obtained using both X-ray emission and photoabsorption spectroscopy techniques. We show that there is general agreement between both sets of data for both alloys. We also point out that the two samples retain a metallic character, yet the hexagonal approximant of the Mg–Zn–Y quasicrystal family is less metallic than the Laves phase. 相似文献
962.
纳米硫化铜近红外吸收材料 总被引:3,自引:1,他引:2
采用新型超声喷雾法技术,把摩尔分数都为0.5%的Cu(NO3)2和Na2S水溶液分别作为初始反应溶液,调节溶液体系的pH值在6~8,把经过超声雾化后的Cu(NO3)2溶液逐步加入到处于强力搅拌的Na2S水溶液中,经陈化过滤后获得纳米半导体硫化铜(CuxS,1≤x≤2)粉体。分析了不同热处理温度与原料配比对获得的硫化铜纳米颗粒化学成分的影响,用X射线粉末衍射仪表征了纳米硫化铜粒子的晶相与化学组成,并采用扫描电镜观察了相应化学组成的粒子晶相形貌,测定了不同化学组分纳米硫化铜粒子从可见到近红外胶体状的吸收和透射光谱。研究表明不同化学组成的纳米硫化铜对近红外光都具有显著的吸收效应,这是由于电子在硫化铜半导体纳米粒子能带中的跃迁所致,同时这些半导体粒子对可见光具有很高透过性,但其可见光透射率随着纳米粒子从Cu2S趋向CuS而略有下降。 相似文献
963.
Mallari A. Naik Satish Patil 《Journal of polymer science. Part A, Polymer chemistry》2013,51(20):4241-4260
The present highlight discusses major work in the synthesis of low bandgap diketopyrrolopyrrole ( DPP )‐based polymers with donor–acceptor–donor ( D–A–D ) approach and their application in organic electronics. It examines the past and recent significant advances which have led to development of low bandgap DPP ‐based materials with phenyl and thiophene as donors. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4241–4260 相似文献
964.
Ching‐Chih Chang Chih‐Ping Chen Ho‐Hsiu Chou Chuang‐Yi Liao Shu‐Hua Chan Chien‐Hong Cheng 《Journal of polymer science. Part A, Polymer chemistry》2013,51(21):4550-4557
Low‐band gap selenophene‐based polymers were synthesized. Their optoelectronic and photovoltaic properties and space‐charge limited currents were compared with those of the related thiophene‐based polymers. The band gaps of the Se‐based derivatives were approximately 0.05–0.12 eV lower than those of their thiophene counterparts. Organic photovoltaic (OPV) devices based on the blends of these polymers and 1‐(3‐methoxycarbonyl)propyl‐1‐phenyl‐[6,6]‐C71 (PC71BM) were fabricated, and the maximum power conversion efficiency of the OPV device based on PSPSBT and PC71BM was 3.1%—with a short‐circuit current density (Jsc) of 9.3 mA cm?2, an open‐circuit voltage (Voc) of 0.79 V, and a fill factor of 0.42—under AM 1.5 G illumination (100 mW cm?2). © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4550–4557 相似文献
965.
Band‐selective excited ultrahigh resolution PSYCHE‐TOCSY: fast screening of organic molecules and complex mixtures 下载免费PDF全文
Jagadeesh Bharatam 《Magnetic resonance in chemistry : MRC》2016,54(4):308-314
Precise assignments of 1H atomic sites and establishment of their through‐bond COSY or TOCSY connectivity are crucial for molecular structural characterization by using 1H NMR spectroscopy. However, this exercise is often hampered by signal overlap, primarily because of 1H–1H scalar coupling multiplets, even at typical high magnetic fields. The recent developments in homodecoupling strategies for effectively suppressing the coupling multiplets into nice singlets (pure‐shift), particularly, Morris's advanced broadband pure‐shift yielded by chirp excitation (PSYCHE) decoupling and ultrahigh resolution PSYCHE‐TOCSY schemes, have shown new possibilities for unambiguous structural elucidation of complex organic molecules. The superior broadband PSYCHE‐TOCSY exhibits enhanced performance over the earlier TOCSY methods, which however warrants prolonged experimental times due to the requirement of large number of dwell increments along the indirect dimension. Herein, we present fast and band‐selective analog of the broadband PSYCHE‐TOCSY, which is useful for analyzing complex organic molecules that exhibit characteristic yet crowded spectral regions. The simple pulse scheme relies on band‐selective excitation (BSE) followed by PSYCHE homodecoupling in the indirect dimension. The BSE‐PSYCHE‐TOCSY has been exemplified for Estradiol and a complex carbohydrate mixture comprised of six constituents of closely comparable molecular weights. The experimental times are greatly reduced viz., ~20 fold for Estradiol and ~10 fold for carbohydrate mixture, with respect to the broadband PSYCHE‐TOCSY. Furthermore, unlike the earlier homonuclear band‐selective decoupling, the BSE‐PSYCHE‐decoupling provides fully decoupled pure‐shift spectra for all the individual chemical sites within the excited band. The BSE‐PSYCHE‐TOCSY is expected to have significant potential for quick screening of complex organic molecules and mixtures at ultrahigh resolution. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
966.
Based on the transfer matrix method (TMM) and Bloch theory, the interaction of elastic waves (normal incidence) with 1D phononic crystal had been studied. The transfer matrix method was obtained for both longitudinal and transverse waves by applying the continuity conditions between the consecutive unit cells. Dispersion relations are calculated and plotted for both binary and ternary structures. Also we have investigated the corresponding effects on the band gaps values for the two types of phononic crystals. Furthermore, it can be observed that the complete band gaps are located in the common frequency stop-band regions. Numerical simulations are performed to investigate the effect of different thickness ratios inside each unit cell on the band gap values, as well as unit cells thickness on the central band gap frequency. These phononic band gap materials can be used as a filter for elastic waves at different frequencies values. 相似文献
967.
968.
在分析计算金属光子晶体的正三角形晶格TE模式的色散特性、全局带隙分布图的基础上,针对TE04模光子晶体谐振腔中仍有较多的模式竞争且金属柱半径较小的问题,结合模式分布特点图,通过优化和选择工作点的位置,将TE04中的竞争模从5种减少为2种,大幅度降低了TE04工作模式中的模式竞争,并且增加了晶格常数和金属柱半径,使之能够承受更大的热损耗,有利于提高腔体功率容量。仿真验证了数值计算的正确性并得出了完整的TE04场分布。 相似文献
969.
《Journal of polymer science. Part A, Polymer chemistry》2018,56(4):430-436
Thienoisoindigo (TIG) moiety has been paid numerous attentions as an excellent acceptor building block in low‐band‐gap polymers. Herein, a new TIG‐dithiophene alternating copolymer (PTIG2T) was successfully synthesized from an asymmetric TIG‐based donor–acceptor (D‐A) monomer via the self‐condensation‐type direct arylation polymerization. PTIG2T exhibited the light absorption over 1000 nm owing to the intramolecular charge transfer in the thin film state, which corresponded to an optical band gap of 1.24 eV. The HOMO and LUMO levels of PTIG2T were determined to be −5.08 and −3.60 eV, respectively. Furthermore, the organic photovoltaic (OPV) with a PTIG2T/PC61BM active layer achieved a power conversion efficiency (PCE) of 3.19%, which is one of the highest PEC achieved by OPVs with TIG‐based materials. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 430–436 相似文献
970.